Snow Size Distribution Parameterization for Midlatitude and Tropical Ice Clouds

2007 ◽  
Vol 64 (12) ◽  
pp. 4346-4365 ◽  
Author(s):  
Paul R. Field ◽  
Andrew J. Heymsfield ◽  
Aaron Bansemer
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Tropical Rainfall Measuring Mission ◽  
Time Averaging ◽  
Size Distributions ◽  
Regional Study ◽  
Ice Clouds ◽  
Microphysical Process ◽  
Ice Water Content ◽  
Ice Water

Abstract Many microphysical process rates involving snow are proportional to moments of the snow particle size distribution (PSD), and in this study a moment estimation parameterization applicable to both midlatitude and tropical ice clouds is proposed. To this end aircraft snow PSD data were analyzed from tropical anvils [Tropical Rainfall Measuring Mission/Kwajelein Experiment (TRMM/KWAJEX), Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE)] and midlatitude stratiform cloud [First International Satellite Cloud Climatology Project Research Experiment (FIRE), Atmospheric Radiation Measurement Program (ARM)]. For half of the dataset, moments of the PSDs are computed and a parameterization is generated for estimating other PSD moments when the second moment (proportional to the ice water content when particle mass is proportional to size squared) and temperature are known. Subsequently the parameterization was tested with the other half of the dataset to facilitate an independent comparison. The parameterization for estimating moments can be applied to midlatitude or tropical clouds without requiring prior knowledge of the regime of interest. Rescaling of the tropical and midlatitude size distributions is presented along with fits to allow the user to recreate realistic PSDs given estimates of ice water content and temperature. The effects of using different time averaging were investigated and were found not to be adverse. Finally, the merits of a single-moment snow microphysics versus multimoment representations are discussed, and speculation on the physical differences between the rescaled size distributions from the Tropics and midlatitudes is presented.

scholarly journals Improved Radar Ice Water Content Retrieval Algorithms Using Coincident Microphysical and Radar Measurements

2005 ◽  
Vol 44 (9) ◽  
pp. 1391-1412 ◽  
Author(s):  
Andrew J. Heymsfield ◽  
Zhien Wang ◽  
Sergey Matrosov
Keyword(s):  
Water Content ◽  
Radar Reflectivity ◽  
Regional Study ◽  
Ice Clouds ◽  
Analytic Expressions ◽  
Ice Water Content ◽  
Particle Ensemble ◽  
Radar Measurements ◽  
Ice Water ◽  
Spaceborne Radar

Abstract Airborne radar reflectivity measurements at frequencies of 9.6 and 94 GHz, with collocated, in situ particle size distribution and ice water content measurements from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in Florida in July 2002, offer one of the first opportunities to evaluate and improve algorithms for retrieving ice water content from single-wavelength spaceborne radar measurements. Both ice water content and radar reflectivity depend on the distribution of particle mass with size. It is demonstrated that single, power-law, mass dimensional relationships are unable to adequately account for the dominating contribution of small particles at lower reflectivities and large particles at higher reflectivities. To circumvent the need for multiple, or complex, mass dimensional relationships, analytic expressions that use particle ensemble mean ice particle densities that are derived from the coincident microphysical and radar observations are developed. These expressions, together with more than 5000 CRYSTAL FACE size distributions, are used to develop radar reflectivity–ice water content relationships for the two radar wavelengths that appear to provide improvements over earlier relationships, at least for convectively generated stratiform ice clouds.

scholarly journals High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

2015 ◽  
Vol 15 (12) ◽  
pp. 16505-16550 ◽  
Author(s):  
A. M. Fridlind ◽  
A. S. Ackerman ◽  
A. Grandin ◽  
F. Dezitter ◽  
M. Weber ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Power Loss ◽  
Deep Convection ◽  
Radar Reflectivity ◽  
Size Distributions ◽  
Stratiform Rain ◽  
Ice Water Content ◽  
Ice Water

Abstract. Occurrences of jet engine power loss and damage have been associated with flight through fully glaciated deep convection at −10 to −50 °C. Power loss events commonly occur during flight through radar reflectivity (Ze) less than 20–30 dBZ and no more than moderate turbulence, often overlying moderate to heavy rain near the surface. During 2010–2012 Airbus carried out flight tests seeking to characterize the highest ice water content (IWC) in such low-Ze regions of large, cold-topped storm systems in the vicinity of Cayenne, Darwin, and Santiago. Within the highest IWC regions encountered, at typical sampling elevations circa 11 km, the measured ice size distributions exhibit a notably narrow concentration of mass over area-equivalent diameters of 100–500 μm. Given substantial and poorly quantified measurement uncertainties, here we evaluate the consistency of the Airbus in situ measurements with ground-based profiling radar observations obtained under quasi-steady, heavy stratiform rain conditions in one of the Airbus-sampled locations. We find that profiler-observed radar reflectivities and mean Doppler velocities at Airbus sampling temperatures are generally consistent with those calculated from in situ size distribution measurements. We also find that column simulations using the in situ size distributions as an upper boundary condition are generally consistent with observed profiles of Ze, mean Doppler velocity, and retrieved rain rate. The results of these consistency checks motivate an examination of the microphysical pathways that could be responsible for the observed size distribution features in Part 2.

scholarly journals Evidence for ice particles in the tropical stratosphere from in-situ measurements

2008 ◽  
Vol 8 (6) ◽  
pp. 19313-19355 ◽  
Author(s):  
M. de Reus ◽  
S. Borrmann ◽  
A. J. Heymsfield ◽  
R. Weigel ◽  
C. Schiller ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Crystal Size ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Water Content ◽  
Tropical Troposphere ◽  
Ice Crystal Size ◽  
Ice Water

Abstract. In-situ ice crystal size distribution measurements are presented within the tropical troposphere and lower stratosphere. The measurements were performed using a combination of a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) which were installed on the Russian high altitude research aircraft M55 "Geophysica" during the SCOUT-O3 campaign in Darwin, Australia. The objective of the campaign was to characterise the outflow of the Hector convective system, which appears on an almost daily basis during the pre-monsoon season over the Tiwi Islands, north of Darwin. In total 90 encounters with ice clouds, between 10 and 19 km altitude were selected from the dataset and were analysed. Six of these encounters were observed in the lower stratosphere, up to 1.4 km above the local tropopause, and were a result of overshooting convection. The ice crystals observed in the stratosphere comprise sizes up to 400 μm maximum dimension, include an ice water content of 0.1×10−3–1.7×10−3 g m−3 and were observed at ambient relative humidities (with respect to ice) between 75 and 157%. Three modal lognormal size distributions were fitted to the average size distributions for different potential temperature intervals, showing that the shape of the size distribution of the stratospheric ice clouds are similar to those observed in the upper troposphere. In the tropical troposphere the effective radius of the ice cloud particles decreases from 100 μm at about 10 km altitude, to 3 μm at the tropopause, while the ice water content decreases from 0.04 to 10−5 g m−3. No clear trend in the number concentration was observed with altitude, due to the thin and inhomogeneous characteristics of the observed cirrus clouds. The ice water content calculated from the observed ice crystal size distribution is compared to the ice water content derived from two hygrometer instruments. This independent measurement of the ice water content agrees within the combined uncertainty of the instruments for ice water contents exceeding 2×10−4 g m−3. Stratospheric residence times, calculated based on gravitational settling only, show that the ice crystals observed in the stratosphere over the Hector storm system have a high potential for humidifying the stratosphere. Utilizing total aerosol number concentration measurements from a four channel condensation particle counter, it can be shown that the fraction of activated ice particles with respect to the number of available aerosol particles ranges from 1:300 to 1:30 000 for tropical upper tropospheric ice clouds with ambient temperatures below −75°C.

scholarly journals Evidence for ice particles in the tropical stratosphere from in-situ measurements

2009 ◽  
Vol 9 (18) ◽  
pp. 6775-6792 ◽  
Author(s):  
M. de Reus ◽  
S. Borrmann ◽  
A. Bansemer ◽  
A. J. Heymsfield ◽  
R. Weigel ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Crystal Size ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Ice Water Content ◽  
Tropical Troposphere ◽  
Ice Crystal Size ◽  
Ice Water

Abstract. In-situ ice crystal size distribution measurements are presented within the tropical troposphere and lower stratosphere. The measurements were performed using a combination of a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP), which were installed on the Russian high altitude research aircraft M55 "Geophysica" during the SCOUT-O3 campaign in Darwin, Australia. One of the objectives of the campaign was to characterise the Hector convective system, which appears on an almost daily basis during the pre-monsoon season over the Tiwi Islands, north of Darwin. In total 90 encounters with ice clouds, between 10 and 19 km altitude were selected from the dataset and were analysed. Six of these encounters were observed in the lower stratosphere, up to 1.4 km above the local tropopause. Concurrent lidar measurements on board "Geophysica" indicate that these ice clouds were a result of overshooting convection. Large ice crystals, with a maximum dimension up to 400 μm, were observed in the stratosphere. The stratospheric ice clouds included an ice water content ranging from 7.7×10−5 to 8.5×10−4 g m−3 and were observed at ambient relative humidities (with respect to ice) between 75 and 157%. Three modal lognormal size distributions were fitted to the average size distributions for different potential temperature intervals, showing that the shape of the size distribution of the stratospheric ice clouds are similar to those observed in the upper troposphere. In the tropical troposphere the effective radius of the ice cloud particles decreases from 100 μm at about 10 km altitude, to 3 μm at the tropopause, while the ice water content decreases from 0.04 to 10−5 g m−3. No clear trend in the number concentration was observed with altitude, due to the thin and inhomogeneous characteristics of the observed cirrus clouds. The ice water content calculated from the observed ice crystal size distribution is compared to the ice water content derived from two hygrometer instruments. This independent measurement of the ice water content agrees within the combined uncertainty of the instruments for ice water contents exceeding 3×10−4g m−3. Stratospheric residence times, calculated based on gravitational settling, and evaporation rates show that the ice crystals observed in the stratosphere over the Hector storm system had a high potential of humidifying the stratosphere locally. Utilizing total aerosol number concentration measurements from a four channel condensation particle counter during two separate campaigns, it can be shown that the fraction of ice particles to the number of aerosol particles remaining ranges from 1:300 to 1:30 000 for tropical upper tropospheric ice clouds with ambient temperatures below −75°C.

scholarly journals High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

2015 ◽  
Vol 15 (20) ◽  
pp. 11713-11728 ◽  
Author(s):  
A. M. Fridlind ◽  
A. S. Ackerman ◽  
A. Grandin ◽  
F. Dezitter ◽  
M. Weber ◽  
...  
Keyword(s):  
Water Content ◽  
Size Distribution ◽  
Power Loss ◽  
Deep Convection ◽  
Radar Reflectivity ◽  
Size Distributions ◽  
Stratiform Rain ◽  
Ice Water Content ◽  
Ice Water

Abstract. Occurrences of jet engine power loss and damage have been associated with flight through fully glaciated deep convection at −10 to −50 °C. Power loss events commonly occur during flight through radar reflectivity (Ze) less than 20–30 dBZ and no more than moderate turbulence, often overlying moderate to heavy rain near the surface. During 2010–2012, Airbus carried out flight tests seeking to characterize the highest ice water content (IWC) in such low-Ze regions of large, cold-topped storm systems in the vicinity of Cayenne, Darwin, and Santiago. Within the highest IWC regions encountered, at typical sampling elevations (circa 11 km), the measured ice size distributions exhibit a notably narrow concentration of mass over area-equivalent diameters of 100–500 μm. Given substantial and poorly quantified measurement uncertainties, here we evaluate the consistency of the Airbus in situ measurements with ground-based profiling radar observations obtained under quasi-steady, heavy stratiform rain conditions in one of the Airbus-sampled locations. We find that profiler-observed radar reflectivities and mean Doppler velocities at Airbus sampling temperatures are generally consistent with those calculated from in situ size-distribution measurements. We also find that column simulations using the in situ size distributions as an upper boundary condition are generally consistent with observed profiles of Ze, mean Doppler velocity (MDV), and retrieved rain rate. The results of these consistency checks motivate an examination of the microphysical pathways that could be responsible for the observed size-distribution features in Ackerman et al. (2015).

Evaluation of Collocated Measurements of Radar Reflectivity and Particle Sizes in Ice Clouds

2011 ◽  
Vol 50 (10) ◽  
pp. 2104-2119 ◽  
Author(s):  
Binod Pokharel ◽  
Gabor Vali
Keyword(s):  
Water Content ◽  
Particle Density ◽  
Radar Data ◽  
Precipitation Rate ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Sampling Locations ◽  
Ice Water Content ◽  
Particle Imaging ◽  
Ice Water

AbstractMeasured 94-GHz reflectivity in midlevel, stratiform ice clouds was compared with reflectivity calculated from size distributions determined with a particle imaging probe. The radar and the particle probe were carried on the same aircraft, the Wyoming King Air, ensuring close spatial correspondence between the two measurements. Good overall agreement was found within the range from −18 to +16 dBZ, but there is an important degree of scatter in the results. Two different assumptions about particle density led to calculated values that bracket the observations. The agreement found for reflectivity supports the use of the data for establishing relationships between the measured reflectivity and ice water content and between precipitation rate and reflectivity. The resulting equation for ice water content (IWC vs Z) agrees with the results of Liu and Illingworth within a factor of 2 over the range of overlap between the two datasets. The equation here reported for precipitation rate (PR vs Z) has a shallower slope in the power-law relationship than that reported by Matrosov as a consequence of sampling particles of greater densities. Because the radar and the particle probe were collocated on the same platform, errors arising from differences in sampling locations and volumes were minimized. Therefore it is concluded that the roughly factor-of-10 spread in IWC and in PR for given Z is, primarily, a result of variations in ice crystal shape and density. Retrievals of IWC and PR from cloud radar data can be expected to have that level of uncertainty.

scholarly journals Relationships between Ice Water Content and Volume Extinction Coefficient from In Situ Observations for Temperatures from 0° to −86°C: Implications for Spaceborne Lidar Retrievals

2014 ◽  
Vol 53 (2) ◽  
pp. 479-505 ◽  
Author(s):  
Andrew Heymsfield ◽  
Dave Winker ◽  
Melody Avery ◽  
Mark Vaughan ◽  
Glenn Diskin ◽  
...  
Keyword(s):  
Water Content ◽  
Extinction Coefficient ◽  
Climate Models ◽  
Detection Threshold ◽  
The Arctic ◽  
Effective Diameter ◽  
Ice Clouds ◽  
Ice Water Content ◽  
Ice Water ◽  
Volume Extinction Coefficient

AbstractAn examination of 2 yr of Cloud–Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) lidar observations and CloudSat cloud radar observations shows that ice clouds at temperatures below about −45°C frequently fall below the CloudSat radar’s detection threshold yet are readily detectable by the lidar. The CALIPSO ice water content (IWC) detection threshold is about 0.1 versus 5 mg m−3 for CloudSat. This comparison emphasizes the need for developing a lidar-only IWC retrieval method that is reliable for high-altitude ice clouds at these temperatures in this climatically important zone of the upper troposphere. Microphysical measurements from 10 aircraft field programs, spanning latitudes from the Arctic to the tropics and temperatures from −86° to 0°C, are used to develop relationships between the IWC and volume extinction coefficient σ in visible wavelengths. Relationships used to derive a radiatively important ice cloud property, the ice effective diameter De, from σ are also developed. Particle size distributions (PSDs) and direct IWC measurements, together with evaluations of the ice particle shapes and comparisons with semidirect extinction measurements, are used in this analysis. Temperature-dependent De(σ) and IWC–σ relationships developed empirically facilitate the retrieval of IWC from lidar-derived σ and De values and for comparison with other IWC observations. This suite of empirically derived relationships can be expressed analytically. These relationships can be used to derive IWC and De from σ and are developed for use in climate models to derive σ from prognosed values of IWC and specified PSD properties.

scholarly journals UARS/MLS Cloud Ice Measurements: Implications for H2O Transport near the Tropopause

2005 ◽  
Vol 62 (2) ◽  
pp. 518-530 ◽  
Author(s):  
D. L. Wu ◽  
W. G. Read ◽  
A. E. Dessler ◽  
S. C. Sherwood ◽  
J. H. Jiang
Keyword(s):  
Water Content ◽  
Total Water ◽  
Ice Clouds ◽  
Clear Sky ◽  
Ice Water Content ◽  
Satellite Microwave ◽  
Cold Point ◽  
Cloud Ice ◽  
Ice Water

Abstract A technique for detecting large hydrometeors at high altitudes is described here and applied to the Upper Atmosphere Research Satellite/Microwave Limb Sounder (UARS/MLS) 203-GHz radiance measurements at tangent pressures between 200 and 46 hPa. At these tangent pressures the radiances remain optically thin and cloudy-sky radiances are brighter than normal clear-sky cases. Unlike infrared/visible cloud observations, the 203-GHz radiances can penetrate most ice clouds and are sensitive to ice crystals of convective origin. Rough ice water content (IWC) retrievals are made near the tropopause using estimated size distributions from in situ convective studies. The seasonal mean IWC observed at 100 hPa reaches vapor-equivalent 20 ppmv or more over convective centers, dominating the total water content. Convectively lofted ice, therefore, appears to be hydrologically significant at the tropical cold point. IWC is well correlated spatially with relative humidity with respect to ice (RHi) at 100 hPa during both the dry (January–March) and moist (July–September) periods.

scholarly journals The Evaluation of CloudSat and CALIPSO Ice Microphysical Products Using Ground-Based Cloud Radar and Lidar Observations

2010 ◽  
Vol 27 (5) ◽  
pp. 793-810 ◽  
Author(s):  
A. Protat ◽  
J. Delanoë ◽  
E. J. O’Connor ◽  
T. S. L’Ecuyer
Keyword(s):  
Water Content ◽  
Statistical Method ◽  
Air Temperature ◽  
Number Concentration ◽  
Effective Radius ◽  
Vertical Profiles ◽  
Statistical Relationship ◽  
Ice Clouds ◽  
Ice Water Content ◽  
Ice Water

Abstract In this paper, the statistical properties of tropical ice clouds (ice water content, visible extinction, effective radius, and total number concentration) derived from 3 yr of ground-based radar–lidar retrievals from the U.S. Department of Energy Atmospheric Radiation Measurement Climate Research Facility in Darwin, Australia, are compared with the same properties derived using the official CloudSat microphysical retrieval methods and from a simpler statistical method using radar reflectivity and air temperature. It is shown that the two official CloudSat microphysical products (2B-CWC-RO and 2B-CWC-RVOD) are statistically virtually identical. The comparison with the ground-based radar–lidar retrievals shows that all satellite methods produce ice water contents and extinctions in a much narrower range than the ground-based method and overestimate the mean vertical profiles of microphysical parameters below 10-km height by over a factor of 2. Better agreements are obtained above 10-km height. Ways to improve these estimates are suggested in this study. Effective radii retrievals from the standard CloudSat algorithms are characterized by a large positive bias of 8–12 μm. A sensitivity test shows that in response to such a bias the cloud longwave forcing is increased from 44.6 to 46.9 W m−2 (implying an error of about 5%), whereas the negative cloud shortwave forcing is increased from −81.6 to −82.8 W m−2. Further analysis reveals that these modest effects (although not insignificant) can be much larger for optically thick clouds. The statistical method using CloudSat reflectivities and air temperature was found to produce inaccurate mean vertical profiles and probability distribution functions of effective radius. This study also shows that the retrieval of the total number concentration needs to be improved in the official CloudSat microphysical methods prior to a quantitative use for the characterization of tropical ice clouds. Finally, the statistical relationship used to produce ice water content from extinction and air temperature obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite is evaluated for tropical ice clouds. It is suggested that the CALIPSO ice water content retrieval is robust for tropical ice clouds, but that the temperature dependence of the statistical relationship used should be slightly refined to better reproduce the radar–lidar retrievals.

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